EXTENDED ISOTROPIC-TO-ANISOTROPIC CROSSOVER ABOVE THE NEMATIC SMECTIC-A PHASE-TRANSITION

We perform a one-loop, self-consistent calculation of the density-wave and director fluctuations above the nematic-smectic-A phase transition, find the renormalization of the perpendicular and parallel correlation lengths, and for the first time calculate values of the anisotropic critical-point exponents nu-parallel-to and nu-perpendicular-to. As the transition is approached several distinct regions of scaling behavior are found with increasingly anisotropic critical behavior. A plot of effective exponents from experiment versus the anisotropy ratio nu-parallel-to/nu-perpendicular-to reveals a systematic correlation that agrees with our calculation.